A wide variety of heart valve prostheses have been developed to operate hemodynamically, in conjunction with the pumping action of the heart, to take the place of defective natural valves. These valves variously have valve bodies which are designed to function either with valve members in the form of a single occluder or in the form of a pair of occluders or leaflets, which valve members pivot along eccentric axes (or both pivot and translate) to open and close a central blood flow passageway through the valve body.
U.S. Pat. No. 4,272,854 (Jun. 16, 1981) shows an early version of a bi-leaflet heart valve having an ear extending from each lateral side of each leaflet, which ear pivots in a recess, guided in part by a knob traveling in a longitudinal slot that is cut more deeply into the sidewall of the valve body.
U.S. Pat. No. 4,373,216 (Feb. 15, 1983) discloses both single occluder and bi-leaflet heart valves wherein protrusions, extending generally radially inward from a pair of flat sidewall sections of the valve body, guide valve members which have slots in their lateral edges to receive such protrusions.
U.S. Pat. No. 4,308,624 (Jan. 5, 1982) discloses heart valves of both the single occluder and bi-leaflet type having curved valve members which both rotate and translate in moving between the open and closed positions. Although the leaflets are intended to be able to assume a parallel orientation in the open position, as shown in FIG. 3, study of the valve arrangement shows that, upon reversal of blood flow through the passageway, the leaflets could translate upstream without beginning to rotate toward the closed position. Although pivoting could occur in the intended manner, once the leaflets have moved upstream (having been guided by the paths the spherical ears trace in the slots 21), one or both of the leaflets might possibly counterrotate, depending upon the instantaneous attitude of bloodstream flow, and thereby not close on that stroke. U.S. Pat. Nos. 4,328,592 and 4,443,894 (Apr. 24, 1984) disclose later versions of this valve. The latter illustrates an embodiment wherein the leaflets in their open position are angled relative to the centerline plane (see Column 4, lines 39-43) so that, when flow reversal occurs (as depicted in FIG. 4), the alignment of angled surfaces 44 of the stops 41 and the placement of the stops is such that inward pivoting or counterrotation of the leaflets is precluded (see Column 5, lines 34-41).
U.S. Pat. No. 4,357,715 shows another embodiment of a heart valve of this general type which has an elongated depression within each slot in the valve sidewall to permit only controlled lateral movement within the slot.
U.S. Pat. No. 4,451,937 (Jun. 5, 1984) shows additional single occluder and bi-leaflet valves wherein valve members are oriented at an angle to the centerline plane in the open position; they pivot and translate to their closed positions guided, in part, by laterally extending ears 21 that move in generally arcuate slots or depressions 23.
U.S. Pat. No. 4,692,165 (Sept. 8, 1987) discloses single occluder and bi-leaflet valves wherein valve members have notches in their lateral edges which receive arcuate posts protruding from flat sidewall sections of the valve body; the posts guide the pivotal and translational movement of the valve members.
U.S. Pat. No. 4,863,458 (Sept. 5, 1989) discloses bi-leaflet heart valves having valve members of varying thickness which are guided in generally pivotal movement by laterally extending ears that are received in recesses formed in the flat sidewall sections of the valve bodies.
Commercially developed heart valves, using valve members of the type very generally exemplified by some of the above-mentioned U.S. patents, have employed those valve members oriented at an angle to the centerline plane in the open position, so that the backflow of blood preferentially impinges upon the outflow surfaces of each valve member and thus initially imparts a pivotal force component in the direction of its closing movement. It is now felt to be particularly important that a mechanical heart valve prosthesis should provide a passageway through which blood can flow freely in the open position with a minimum of drag. To accomplish this desired objective, it is now believed that the valve members should be able to assume an orientation which is parallel to the longitudinal axis of the passageway; however, in such orientation, it is important that the valve members should still be highly responsive to backflow so as to close quickly with a minimum of regurgitation. Improvements in valve construction have continued to be sought with the objective of creating mechanical valves having such characteristics.